The development of perfusion bioreactor systems for long term maintenance of functional hepatic culture with a strong predictive power for in vitro drug testing is one of the challenging tasks facing bioengineers (Brandon, E F, Raap, C D, et al., Toxicol Appl Pharmacol (2003) 189, 3, 233-246). Primary hepatocytes lose their liver-specific functions upon isolation as a result of the disintegration of in vivo micro-environment characterized by cell-cell interaction, cell-matrix interaction and maximal mass transport. Several methods have been proposed to overcome the loss of cell functionality through the re-establishment of in vivo-like micro-environment for the primary hepatocytes, by using semi-permeable hollow fiber membranes, gel encapsulations, or porous scaffolds. Cell immobilization can be achieved by means of micro-carrier or suspended in collagen gel matrix to form culture of 2D, 3D or spheroids configurations (Landry, J, Bernier, D, et al. J Cell Biol (1985) 101, 3, 914-923; Kan, P, Miyoshi, H, et al. (2004) Tissue Eng 10, 9-10, 1297-1307; Park, J, Berthiaume, F, et al. Biotechnol Bioeng (2005) 90, 5, 632-644; Park, J., Li, Y, et al., Biotechnol Bioeng (2008) 99, 2, 455-467).
Studies have shown that sandwich culture provides microenvironment mimicry of the situation found in vivo. This culturing method provides anchorage for hepatocyte attachment and the establishment of hepatic polarity through the formation of bile canalicular network between contiguous cells, while maintaining the cells' biliary excretion function. Du Y et al reported the re-establishment of hepatic polarity and long-term maintenance of in vitro hepatic functions through the use of bioactive-synthetic materials for their 3D hepatocyte monolayer sandwich culture. The study indicated that the synthetic 3D monolayer culture exhibited a similar process of hepatic polarity formation, better cell-cell interaction and improved differentiated functions over 14-day culture compared to the hepatocytes in collagen sandwich culture. The study highlighted that this technique is ideally suited for liver tissue engineering applications such as drug metabolism/toxicity testing (Dunn, J C, Tompkins, R G, et al. Biotechnol Prog (1991) 7, 3, 237-245; Kern, A, Bader, A, et al. Biochem Pharmacol (1997) 54, 7, 761-772; De Smet, K., Bruning, T, et al. Arch Toxicol (2000) 74, 10, 587-592; Kemp D C, Brouwer, K L, Toxicol In Vitro (2004) 18, 6, 869-877; Kemp, D C, Zamek-Gliszczynski, M J, et al. Toxicol Sci (2005) 83, 2, 207-214)
To maintain cell viability and liver-functions in the primary hepatocytes culture, the application of perfusion bioreactors has been indispensable. Research has demonstrated that perfusion bioreactors enhance mass transport of dissolved oxygen and nutrients to the cell culture, thereby enabling their viability and function (Rotem, A, Toner, M, et al. Biotechnol Bioeng (1994) 43, 7, 654-660; McClelland, R E, Coger, R N, Tissue Eng (2004) 10, 1-2, 253-266). However, many of the existing in vitro perfusion drug testing platforms suffer from the ability to maintain long term cell viability and liver-specific functions. In addition, many of their designs do not conform to the standard cell culture plate dimension, making the transferability of cell cultures to other standard drug testing platforms inconceivably difficult.
There remains therefore a need for a culture platform that addresses the current drawbacks in existing in vitro drug testing bioreactor design.
Accordingly it is an object of the present invention to provide a device or apparatus that overcomes at least some of these drawbacks. This object is solved by providing an apparatus according to claim 1.